jerome951

I don't think anyone has answered George's initial question of max canister pressure. The literature that came with mine stated 300 psi was max.

Acropora

My understanding is that you want the cannister pressures as low as possible w/o allowing the fluid in the shocks to bubble under use?

CarreraCup03

I have 175 lbs in front and 280 lbs in the rear moton cs. springs are 700 lbs spring front and 900 lbs in the rear. 2650 lbs car. The car handles fantasticly! Of course there are many more variables ... tires, wheels, sways, and allignment settings ... but it is a good place to start.

Greg Fishman

Hank,
FWIW I ran 1100 and 1250 in my 993 with D/A JRZs. Pressures in the 180lb range.

George A

Hank,

Our cars are similar. It’s a track only car but it’s fairly stock with the exception of suspension. I just added the full ERP monoball setup that I got from viperbob. Other than that, everything else is stock. I even still have the cd changer in the trunk. I wanted to stay in D for PCA CR so I haven’t touched anything. I still have the original cats (but I did just get a set of bypass pipes), a/c, carpet, etc. I have to be at 3064 lbs and I still have to add about 50 lbs to get there. I don’t have a cage yet (it was supposed to be installed over the winter but there was too much going on at the shop and the car so I’m holding off until the end of May), I’m using the DAS bar for now so I have the same issue with chassis flex.

I’m following the PCA rules to a T, I don’t want to leave anything up for interpretation. That makes my setup even more difficult. I can’t use the RS uprights, so I decided to go as stiff as possible to minimize suspension travel hoping to eliminate bump steer and the kinematic toe effect (just my theory, I could be wrong).

Now, I don’t claim to know anything about suspension setup above the basics, but a couple of things I learned from my previous setups were that the 200lbs spread front to back and the 1 degree slope did not work for me. For me, the best spread was between 100 to 150 lbs front to rear. Also, I had the slope at 0.5 degrees and am now about to try it with no slope. I had the same oversteer issues you describe until I changed to the above.

Hope that helps.

George

CarreraCup03

Keep in mind the Moton Club Sports have a smaller piston rod in the rear so they need more pressure to compensate for this. So you cant compare the rear pressures with JRZ or even the Moton Full Race. Think the front pistons are the same size but the rears are smaller ... thus the higher pressure in the rear of the Moton CS

Hank Cohn

George,

Our cars are very similar. Mine is a C-Stock car. I also have the DAS bar. My car is a non-sunroof car so my roll bar is slightly taller than your and commensurately heavier. The car’s weight is 2900 lbs. Without removing door bars, cats and mufflers, front and rear bumper supports and A/C, I think my car is as light as it is going to get. It does look like there is a Cargraphic N-GT muffler and 100 cell cat system that is significantly lighter than the stock setup at just over $4000.00!

My car does have a 3.8 and RS gearbox and almost every other RS bit available. I didn't realize that RS uprights were not D-Stock legal. That must mean that they change the suspension geometry. For the record I ran a previous 993 in D and C with stock uprights and never had a problem with bump steer. It had 1100 and 1300 lb springs.

The test doesn't begin until later today if you are wondering why I am typing and not driving. I'll be leaving work around 3:00 this afternoon.

Thanks for your thoughts about the setup, spring split and slope. I am trying to remain uninvolved and stick with the testing program laid out by the guys doing the work on the car. I know this is a mixed bag, but it has been interesting to make small changes - one at a time and see what the effect of that change is. In an earlier post you said that you sometimes do the opposite of what "they" say. One of the most interesting aspects of my testing so far has been stiffening the rear to reduce oversteer. I would have done the opposite (in fact, I did) but it has gotten much better. I did find an official Moton brochure which gave a maximum canister pressure for the front struts as being 20 bar - or nearly 300 psi. It didn't give a max pressure for the rear shock, but I would assume that it would be the same or very similar.

Hank

coryf

In the near future, the Moton CS will get the larger shaft in the rear like the Race shocks.
In my experience, fronts can be run from 100-200psi and the rears 175-275psi with the smaller rear shaft (and about 25psi lower with the larger shaft). Car weight, spring rate and bumpiness of the track factor into canister pressure.
Shock canister pressure should always be set cold (not heated up by engine, brakes, etc) with the wheel unloaded (on air jacks or jack stands - on the ground will be about 20psi higher)

Alan C.

Hank,
I made a mistake on my springs. The fronts were 900 and the rears 1000.
Dave Schardt thought the setup was pretty good.

Hank Cohn

George, et al,

The test day was not as revealing as it might have been. I thought the Michelin Pilot Sport Cups had a lot more life left in them than they actually had. In retrospect, I am frustrated that I went to all the trouble and expense to get another test day and didn’t bring new tires.

That aside, the car still exhibited some oversteer, however, it was much more controllable than before the spring change. Nic Johnsson was there and drove the car again and he even backed off the compression a few clicks at the rear which further improved the balance of the car. We decided not to make any further adjustments until I mount new tires. It could be, and, I hope it is, that the car will be very neutral with said new set of tires.

The track, Road Atlanta, was available to us from 5:00 PM to 8:00 PM. The temperature during the day had been in the upper 80s and was still 87 degrees at 5:30. As far as I know the track had not been used that day. If so, it was by the Panoz racing school. I don’t know if a track is faster or slower in the late afternoon but by the time we started taking times, my tires were in poor condition. The fastest lap on the display was a 1:41.9 with a lot of 1:42s, which is significantly slower by 2.5 seconds than the fastest laps three weeks ago with new tires and a worse handling car. In all fairness the temperature was in the upper 60s on the last test day.

The most optimistic result would be that:
1. A track in the late afternoon is at its worst.
2. My tires were really in poor shape.
3. Only a skilled driver could get a 1:41 under those conditions. (VERY optimistic!)

There will be another opportunity to test in 3 weeks. If anyone is interested, I’ll post some results.

95m3racer

Hank, what spec is your car? (i see c-stock, but is it maxed to the rules, or whats its exact config,2900lbs, what hp?)

Pro's in BMW's in WC are 290hp and 2600-2800lbs and usually run 1:34-1:35 in good conditions, but thats on RA-1's.

Amatuer's in BMWCCA guys with 320hp and 2500# and slicks are running 1:33-1:35.

here are PCA results from April.

http://mylaps.com/results/showevent.jsp?id=122984

Some FAST cars.

George A

Hank, please do let me know how your next testing session goes. I'm very interested.

95m3racer, our cars are similar to what would be in STOCK or PREPARED classes in BMW CCA. Look at the times of any of the xS and xP for RA, nothing below 41's. Hell, the only IP car that got below the 40's was busted for an illegal engine. Several of my buddies raced there last year. You can't really compare a C mod or D mod car's times to ours, remember you are talking about street legal cars here.

George

Hank Cohn

95m3racer,

You nailed it. It is a c-stock car not maxed to the rules mostly by weight. The car is 100 lbs. over weight and that extra weight is in the cat, mufflers, heat exchangers (exhaust headers) and A/C. The suspension is still all rubber with the exception of the monoball spring mounts. This car has done 1:37s at Road Atlanta before on Michelin Pilot Sport Cups. It is a long story, but we’ve never been able to get back to those times.

The car weighs 2920 lbs, makes 300 HP and runs on the aforementioned Michelin tires sized 225 fronts and 265 rears. I always hate to post a time because it is mostly irrelevant without seeing what the competition is doing on that track on that day at that time.

From your prior posts, I sense that you have a much better grasp of the technical aspects of racing than I do. I have relied on the expertise of others for a long time in this sport to set up my car, and, at times, have had great cars to drive and at other times I’ve had setups that were all but undriveable.

As I stated earlier, it was a real shame to waste a testing opportunity by not having a new set of tires. Lesson learned!

Hank

95m3racer

Yep, I was assuming it was not a mod car, If anything it was a compliment to how fast porsches can be

Just watch out for the new E46 M3 prepared cars...they are running FAST!

And when this Z4M comes out and is spec'd, it's going to be tough to beat.

And as far as my technical experience, i'm a mechanical engineer (with motorsports and manufacturing concentrated).

I'm merely comparing it to BMWCCA cars to give me an idea of how fast your cars are, since recently I know BMWCCA cars best. A couple of us engineers at a company in VA built a car last yearm designed it from scratch based of a 95 m3 ltw, and with a pretty much stock motor took a bunch of overall wins and fastest laps, including overall win at Oktoberfest in the sprint and endurance race, against a v8 m3 gtr, and a couple pro teams running thier GAC/WC cars. Trying to guage how fast some of the recent P-car's are that my new e46 m3 project would run with.

George A

You mean like this?

George